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Slow motion with compositions

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Paxson Woelber
Slow motion with compositions
on Jan 6, 2011 at 8:15:48 pm

Hi, I have a question about applying a slow-mo effect to an animated scene that includes many compositions. Here's the scene: It's about a dozen people riding horses riding across the frame, and each horse is a composition made up of about 40 individual pieces that's been placed into the scene.

I would like a way to play the scene at regular speed and then snap into slow-mo for a few seconds. So, the motion of the scene itself would have to slow down, and the motion of all of the compositions contained in the scene would have to slow down too. Any suggestions?


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Dave LaRonde
Re: Slow motion with compositions
on Jan 6, 2011 at 8:55:04 pm

Before we can give you a truly useful answer, we'd need more information: specifically, how these 40 equestrians made it to your comp.

Was it a single, elaborate shot? Animated stills? Layers with Puppet tool attached?

It makes a difference in the quality of the slo-mo. Any frame rate info you can provide would be helpful, too.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Paxson Woelber
Re: Slow motion with compositions
on Jan 6, 2011 at 9:18:03 pm

Thanks for your quick response, Dave. Each "equestrian" consists of hand-drawn pieces cut into about 40 different layers and animated into a running cycle using the parent tool.

Here is a (slightly unfinished) view of the "equestrian" (as you can see, it's not quite a horse, but I thought that would be the best way to describe it as far as getting help):


I plan on having about 40 of these guys running through a scene at one.


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Todd Kopriva
Re: Slow motion with compositions
on Jan 6, 2011 at 9:31:27 pm

You can time-remap the composition that contains the whole scene.

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Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
Premiere Pro Help & Support
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Paxson Woelber
Re: Slow motion with compositions
on Jan 6, 2011 at 9:45:16 pm

Thank you, Todd. Will that remap all of the compositions nested in that scene?


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Todd Kopriva
Re: Slow motion with compositions
on Jan 6, 2011 at 9:50:10 pm

> Will that remap all of the compositions nested in that scene?


Yes.

Regarding the frame-rate concerns that Dave is alluding to: Keep in mind that slowing something down means that the software has to interpolate (make up) image data for the frames in between the original frames. You have frame blending controls to determine how this is done, but even the highes-quality frame blending mode (pixel motion) can't work magic, so if you slow something down too much, you may get lousy results.

---------------------------------------------------------------------------------------------------------
Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
Premiere Pro Help & Support
---------------------------------------------------------------------------------------------------------


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Paxson Woelber
Re: Slow motion with compositions
on Jan 6, 2011 at 9:52:30 pm

Ok, thanks very much for the help. I'll run some tests and see if I can work it out. Regards,
Paxson.


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Paxson Woelber
Re: Slow motion with compositions
on Jan 7, 2011 at 4:35:22 am

Todd and Dave thank you both for the help. The process worked perfectly, and the nested/precomposed animations were all slowed down correctly. One hurdle down. One more to go:

It looks like the motion blurs were remapped as well, so that when the action slows down the appearance of the motion blurs becomes very pronounced. (All of the motion blurs are added in AfterFX - this is all 2D animation so there is no natural blurring in footage here). Is there any way to keep the motion blurs consistent even when the scene is remapped? Perhaps a way to tween the shutter angle for the composition? My only thought here is to add a motion blur in post-production to the flattened scene, but that seems less than ideal.

I hope I'm articulating this problem clearly, if not please let me know, and thank you both again for the help - I really appreciate it.


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Dave LaRonde
Re: Slow motion with compositions
on Jan 7, 2011 at 5:19:02 pm

If the change from normal motion to slo-mo and back to normal speed is instantaneous, I have a suggestion... but if you're ramping the speed up & down, it gets iffy. Here goes:

You know those 40 nested comps with the animals & riders? I'd bet some of them are duplicated layers: you have less than 40 variants. In the project window, duplicate each variant, open it and turn off motion blur.

Now in the main comp, duplicate all of those nested comp layers. Use the Replace Footage command to replace a newly-duplicated layer with its no-motion-blur counterpart; it will assume all the attributes of the layer it replaces: any animated values, any effects, and especially time remapping.

When done, trim the in & out points of these layers so that you see the motion-blurred ones at normal speed, and the non-motion-blurred ones when it changes to slo-mo.

That's a bunch of work, so I'd be interested to know if there's an easier way to skin this particular cat. But it will do the trick for you.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Spencer Tweed
Re: Slow motion with compositions
on Jan 6, 2011 at 9:39:22 pm

It is quite simple. To elaborate on what the Adobe guy said, you take all of those and stick them in comp A. Then put comp A into comp B (precompose it, in other words). Inside comp B you animate the time-remap values.

Andrew Kramer (videocopilot.net) has a few tutorials on this. Check them out, you can always learn a few things from him.

- Spencer


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Dave LaRonde
Re: Slow motion with compositions
on Jan 6, 2011 at 9:46:18 pm

[Spencer Tweed] "To elaborate on what the Adobe guy said, you take all of those and stick them in comp A. Then put comp A into comp B (precompose it, in other words). Inside comp B you animate the time-remap values."

That's correct. But we know NOTHING about the footage involved. We don't know if it's video. We don't know if it's progressive scan, interlaced or progressive segmented frame. We don't know the frame rate. If some of it is video, you have to be very careful about applying time remapping or you'll get less than desirable results.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Paxson Woelber
Re: Slow motion with compositions
on Jan 6, 2011 at 9:51:45 pm

Sorry, to clarify, all of the material used in the piece is hand-drawn. There's no video footage at all. It's entirely hand-drawn and then animated in AfterFX. The frame rate I'm using for the animation is 29.97, though.

If I precompose and then time remap, won't it give me a somewhat sub-par result? I mean, since I'm working at 29.97, if I want to slow it down 300% won't the remapping process be taking 29.97 footage and then just blending individual frames?

Here's another frame:


I guess what I'm asking is, is there a way to make the remapping process remap all of the nested compositions at the same time?


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Todd Kopriva
Re: Slow motion with compositions
on Jan 6, 2011 at 9:53:29 pm

Why don't you just increase the frame rate of your nested component compositions?

---------------------------------------------------------------------------------------------------------
Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
Premiere Pro Help & Support
---------------------------------------------------------------------------------------------------------


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Dave LaRonde
Re: Slow motion with compositions
on Jan 6, 2011 at 10:13:08 pm

Glad to know there are no frame rates involved with the footage. As usual, Todd's on the money: just increase the frame rate of your nested comps. It won't do any harm, you won't have to move any keyframes, and it will result in much better-looking slo-mo in the 29.97 master comp.

AE can accommodate frame rates up to and including 99fps.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Kevin Camp
Re: Slow motion with compositions
on Jan 6, 2011 at 10:46:04 pm

if all your animations are keyframed within the comps (ie. nothing pre-rendered) then you shouldn't have to change any frame rates. time remapping will interpolate the new keyframed data just fine. it won't look jerky or have artifacts or have any problems that frame/pixel interpolation can have when you try to slow down actual footage.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW


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Spencer Tweed
Re: Slow motion with compositions
on Jan 7, 2011 at 1:21:50 am

What you are saying is that if you collapse transformations on a pre-comped layer that has time remapping it will basically adjust keyframes instead of interpolating new images? I've wondered about this but haven't had a chance to test it.

- Spencer


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Kevin Camp
Re: Slow motion with compositions
on Jan 7, 2011 at 3:56:09 pm

you don't even have to use collapse transformations, time remapping will recalculate the interpolation between keyframes at a new rate for every keyframed property in the nested comp.

if you wanted to try a quick test, just crate a simple comp with a layer that moves across the screen. choose layer>pre-compose (move all attributes) and then enable time remapping and change the remapping. the layer should move at a different rate, but it should be as smooth as if you have modified the position keyframes.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW


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Spencer Tweed
Re: Slow motion with compositions
on Jan 6, 2011 at 11:03:42 pm

Hey Dave,

Sorry to throw this back at you, but what does any of that matter? Interlaced or progressive doesn't make a difference as long as he is interpolating it correctly because After Effects just builds whole frames out of the fields anyway. Frame rate shouldn't change anything unless he is working with something crazy (as far as I know, anyway. Correct me if I'm wrong). Other than that the only thing I can think of that would throw off the pixel blending is a 3:2 pulldown, which I haven't tried before but I would hope that After Effects could handle this in a similar way that it deals with fields.

Progressive segmented frames don't apply because the only time you would see this in After Effects is during rendering; in other words after the time remap has been calculated.


All that said, you are right - it would be easier if we knew the exact situation and footage involved.


- Spencer


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Dave LaRonde
Re: Slow motion with compositions
on Jan 7, 2011 at 12:07:49 am

[Spencer Tweed] "Interlaced or progressive doesn't make a difference as long as he is interpolating it correctly because After Effects just builds whole frames out of the fields anyway."

Yes, it will... however, it will use what's available to build that frame, which is one field, which contains half the vertical resolution. I'm not saying you have to avoid time remapping interlaced footage as if the effect carries the ebola virus, I'm saying you have to be careful and judicious in its use.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Spencer Tweed
Re: Slow motion with compositions
on Jan 7, 2011 at 1:22:47 am

So you are saying it will just have half of the data to interpolate with?

- Spencer


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Dave LaRonde
Re: Slow motion with compositions
on Jan 7, 2011 at 4:33:54 pm

Indeed I am. That's why pricey plugins exist to change the speed of a shot.

To slow down a shot, they use proprietary algorithms to interpolate the image's motion from one frame to the next, then reconstruct a brand-new intermediate frame (or frames) in full horizontal and vertical resolution.
Because there are many forms of motion -- the camera can move, the subject can move, both can move, the basic direction of movement can vary widely -- there are a number of algorithms from which to choose. If you decide to slow down a shot by a large amount, the number of intermediate frames to be created increases, and the accuracy of the interpolation drops: you create additional frames, but use the same two data points, the preceding and following frame.

That's why nothing -- neither hardware nor software -- will ever be able to create silky-smooth, good-looking super-slo-mo from footage shot at a normal frame rate. That's why, if you need slo-mo, the best policy is to shoot at a higher frame rate.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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